Biosensor

ABSTRACT

A biosensor system includes an array of biosensors with a plurality of electrodes situated proximate the biosensor. A controller is configured to selectively energize the plurality of electrodes to generate a DEP force to selectively position a test sample relative to the array of biosensors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 17/818,573,filed Aug. 9, 2022, which is a division of U.S. application Ser. No.17/172,161, filed Feb. 10, 2021, and titled “BIO SENSOR,” thedisclosures of which are hereby incorporated by reference.

BACKGROUND

Biosensors refer to devices for sensing and detecting biomolecules andoperate on the basis of electronic, electrochemical, optical, andmechanical detection principles. Biosensors that include transistors aresensors that electrically sense charges, photons, and mechanicalproperties of bio-entities or biomolecules. The detection can beperformed by detecting the bio-entities or biomolecules themselves, orthrough interaction and reaction between specified reactants andbio-entities/biomolecules. Such biosensors can be manufactured usingsemiconductor processes, can quickly convert electric signals, and canbe easily applied to integrated circuits (ICs) andmicroelectromechanical systems (MEMS).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion. In addition, the drawings are illustrative as examples ofembodiments of the invention and are not intended to be limiting.

FIG. 1 is a block diagram illustrating aspects of an example biosensorsystem in accordance with some embodiments.

FIG. 2 is a block diagram schematically illustrating an example of abioFET in accordance with some embodiments.

FIG. 3 is a sectional side view illustrating aspects of a backsidesensing bioFET device in accordance with some embodiments.

FIG. 4 is a flow diagram illustrating a method for 3D analysis of a testsample using a 2D biosensor device in accordance with some embodiments.

FIGS. 5A-5C are block diagrams illustrating aspects of the method shownin FIG. 4 in accordance with some embodiments.

FIG. 6 is a top view illustrating aspects of an example biosensor devicein accordance with some embodiments.

FIG. 7 is a top view illustrating further aspects of the examplebiosensor device shown in FIG. 6 in accordance with some embodiments.

FIG. 8 is a sectional side view illustrating further aspects of theexample biosensor device shown in FIGS. 6 and 7 in accordance with someembodiments.

FIG. 9 is a block diagram conceptually illustrating a positivedielectrophoresis (DEP) force acting on a test sample in accordance withsome embodiments.

FIG. 10 is a block diagram conceptually illustrating a negative DEPforce acting on a test sample in accordance with some embodiments.

FIG. 11 is a block diagram illustrating an example of electrodeactivation to generate a DEP force in accordance with some embodiments.

FIG. 12 is a block diagram illustrating another example of electrodeactivation to generate a DEP force in accordance with some embodiments.

FIG. 13 is a block diagram illustrating another example of electrodeactivation to generate a DEP force in accordance with some embodiments.

FIG. 14 is a block diagram illustrating another example of electrodeactivation to generate a DEP force in accordance with some embodiments.

FIG. 15 is a block diagram illustrating another example of electrodeactivation to generate a DEP force in accordance with some embodiments.

FIGS. 16-20 illustrate an example of a process for forming electrodesfor the biosensor device shown in FIGS. 6-8 in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In general, as used herein a “biosensor” refers an analytical deviceused for the detection of a chemical substance that combines abiological component with a physicochemical detector. Such biologicalcomponents may include, for example, cells, groups of cells, tissue,microorganisms, organelles, cell receptors, enzymes, antibodies, nucleicacids, etc. Such biologically derived materials or biomimetic componentsinteracts with, binds with, or recognize the analyte under study.

The term “bioFET” as used herein refers to a field-effect sensor with asemiconductor transducer, and more particularly to a field-effecttransistor (FET) based biosensor. In a bioFET, the gate of ametal-oxide-semiconductor field-effect transistor (MOSFET), whichcontrols the conductance of the semiconductor between its source anddrain contacts, is replaced by a bio- or biochemical-compatible layer ora biofunctionalized layer of immobilized probe molecules that act assurface receptors. Essentially, a bioFET is a field-effect biosensorwith a semiconductor transducer. A decided advantage of bioFETs is theprospect of label-free operation. Specifically, bioFETs enable theavoidance of costly and time-consuming labeling operations such as thelabeling of an analyte with, for instance, fluorescent or radioactiveprobes.

A typical detection mechanism for bioFETs is the conductance modulationof a transducer due to the binding of a target biomolecule or bio-entityto a sensing surface or a receptor molecule immobilized on the sensingsurface of the bioFET. When the target biomolecule or bio-entity isbonded to the sensing surface or the immobilized receptor, the draincurrent of the bioFET is varied by the potential from the sensingsurface. This change in the drain current can be measured and thebonding of the receptor and the target biomolecule or bio-entity can beidentified. A great variety of biomolecules and bio-entities may be usedto functionalize the sensing surface of the bioFET such as ions,enzymes, antibodies, ligands, receptors, peptides, oligonucleotides,cells of organs, organisms and pieces of tissue. For instance, to detectssDNA (single-stranded deoxyribonucleic acid), the sensing surface ofthe bioFET may be functionalized with immobilized complementary ssDNAstrands. Also, to detect various proteins such as tumor markers, thesensing surface of the bioFET may be functionalized with monoclonalantibodies.

Biosensors are typically used for two-dimensional (2D) analysis of atest sample, such as a cell culture. However, three-dimensional (3D)cell analysis is desirable to obtain additional information regardingthe test sample. As compared to typical 2D cell cultures, 3D cellanalysis may provide more relevant information. For instance, an arrayof 2D electrodes or image sensors may be used to monitor a 3D cell.However, such arrangements only get partial information from sub-cellsthat actually contact the 2D biosensor surface. It may be difficult toget an accurate behavioral profile of a whole 3D cell based on thisincomplete information.

In accordance with aspects of the present disclosure, 3D cells to beanalyzed are manipulated on a semiconductor biosensor platform usingtechniques such as dielectrophoresis (DEP) to analyze the entire 3Dcell. Such DEP techniques, for example, may be configured to trap, lift,and rotate 3D cells for monitoring and analysis with a semiconductorbiosensor platform. In general, DEP refers to a phenomenon wherein aforce is exerted on a dielectric particle when it is subjected to anon-uniform electric field. This force does not require the particle tobe charged. Manipulation of cells using DEP in embodiments disclosedherein provides a methodology to achieve 3D electrical cell detectionusing a 2D sensor.

FIG. 1 is a block diagram of an example biosensor system 100 inaccordance with the disclosure. As shown in FIG. 1 , the examplebiosensor system 100 may include, among other things, a sensor array102, a fluid delivery system 104, an electrode array 106 and acontroller 108. The sensor array 102 may have at least one sensingelement for detecting a biological or chemical analyte.

The sensor array 102 may include an array of bioFETs 110, an example ofwhich is illustrated in FIG. 2 . The bioFET 110 shown in FIG. 2 may befunctionalized to detect a particular target analyte, and different onesof the sensors may be functionalized using different capture reagentsfor detecting different target analytes. The bioFETs may be arranged ina plurality of rows and columns, forming a 2-dimensional array ofsensors. In some embodiments, each row of bioFETs is functionalizedusing a different capture reagent. In some embodiments, each column ofbioFETs is functionalized using a different capture reagent.

The fluid delivery system 104 may deliver one or more fluid samples tothe sensor array 102. The fluid delivery system 104 may be amicrofluidic well positioned above the sensor array 102 to contain afluid over the sensor array 102. The fluid delivery system 104 may alsoinclude microfluidic channels for delivering various fluids to thesensor array 102. The fluid delivery system 104 may include any numberof valves, pumps, chambers, channels designed to deliver fluid to thesensor array 102. The electrode array 106 may include a plurality ofelectrodes configured to manipulate a sample to be analyzed by thesensor array, such as cells.

The controller 108 may send and receive electrical signals to both thesensor array 102 and the electrode array 106 to position the sample asdesired to perform bio- or chemical-sensing measurements. The controller108 may also send electrical signals to the fluid delivery system 104to, for example, actuate one or more valves, pumps, or motors. Thecontroller 108 may include one or more processing devices, such as amicroprocessor, and may be programmable to control the operation of theelectrode array 106, the sensor array 102 and/or the fluid deliverysystem 104. Examples of various electrical signals that may be sent andreceived from sensor array 102 will be discussed in more detail below.

The example bioFET 110 may include, among other things, a vertical fluidgate (VFG) 112, a source region 114, a drain region 116, a sensing film118, and a channel region 120. The fluid delivery system 104 applies afluid 122 over the sensing film 118. The fluid 122 may contain analyte.The sensing film 118 may be an electrically and chemically insulatinglayer that separates the fluid 122 from the channel region 120. Thesensing film 118 may include, among other things, a layer of a capturereagent. The capture reagent is specific to an analyte and capable ofbinding the target analyte or target reagent. Upon binding of theanalyte, changes in the electrostatic potential at the surface of thesensing film 118 occur, which in turn results in an electrostatic gatingeffect of the bioFET 110, and a measurable change in a current betweenthe source and drain electrodes (e.g., an Ids current 126). A voltageapplied to the vertical fluid gate 112 may also change the Ids 126. Inother words, the output signal of the bioFET 110 is the Ids 126 whichhas a relationship with the voltage applied to the vertical fluid gate112. In one embodiment, the bioFET may be a dual-gate back-side FETsensor, though other types of bioFETs are within the scope of thedisclosure.

FIG. 3 illustrates a backside sensing bioFET device 130 in accordancewith some disclosed embodiments. A back-end-of-line (BEOL) interconnectstructure 136 is arranged over a handling substrate 138 and a devicesubstrate 134 is arranged over the BEOL interconnect structure 136. Areference electrode 132 is arranged over the device substrate 134. Thehandling substrate 138 may be, for example, a bulk semiconductorsubstrate, such as a bulk substrate of monocrystalline silicon.

The interconnect structure 136 may include a multi-layer interconnect(MLI) structure having conductive lines, conductive verticalinterconnect accesses (vias), and/or interposing dielectric layers(e.g., interlayer dielectric (ILD) layers). The interconnect structure136 may provide various physical and electrical connections to thebioFET 110. The conductive lines may comprise copper, aluminum,tungsten, tantalum, titanium, nickel, cobalt, metal silicide, metalnitride, poly silicon, combinations thereof, and/or other materialspossibly including one or more layers or linings. The interposingdielectric layers (e.g., ILD layers) may comprise silicon dioxide,fluorinated silicon glass (FGS), SILK (a product of Dow Chemical ofMichigan), BLACK DIAMOND (a product of Applied Materials of Santa Clara,Calif.), and/or other suitable insulating materials. The MLI structuremay be formed by suitable processes typical in CMOS fabrication such asCVD, PVD, ALD, plating, spin-on coating, and/or other processes.

The device substrate 134 accommodates the bioFET 110 and may be, forexample, a semiconductor layer of a semiconductor-on-insulator (SOI)substrate or a bulk semiconductor substrate. The bioFET 110 comprises apair of source/drain regions 114, 116 and, in some embodiments, a backgate electrode 148. The source/drain regions 114, 116 have a firstdoping type and are arranged within the device substrate 134,respectively on opposite sides of a channel region 120 of the bioFET110. The channel region 120 has a second doping type opposite the firstdoping type and is arranged in the device substrate 134, laterallybetween the source/drain regions 114, 116. The first and second dopingtypes may, for example, respectively be n-type and p-type, or viceversa. In some embodiments, the bioFET 110 is arranged through thedevice substrate 134 extending from a top surface of the devicesubstrate 134 to a bottom surface of the device substrate 134 as shown.In some other embodiments, the source/drain regions 114, 116 and thechannel region 120 are arranged at an underside of the device substrate134 (lower portion of the device substrate 134). In some embodiments,the bioFET 110 is arranged within a well region 140 of the devicesubstrate 134 that has the second doping type, and/or are electricallycoupled to the BEOL interconnect structure 136. The back gate electrode148 is arranged under the device substrate 134, laterally between thesource/drain regions 114, 116, and is spaced from the device substrate134 by a gate dielectric layer 142 of the bioFET 110. In someembodiments, the back gate electrode 148 is electrically coupled to theBEOL interconnect structure 136 and/or is metal, doped polysilicon, or acombination thereof.

An isolation layer 144 is arranged over the device substrate 134, andcomprises a sensing well 146. The sensing well 146 extends into theisolation layer 144 to proximate the channel region 120 and is at leastpartially lined by a bio-sensing film 118. Further, in some embodiments,the sensing well 146 extends through the isolation layer 144 to exposethe channel region 120 and/or is arranged laterally between thesource/drain regions 114, 116. In some embodiments, the sensing well 146and the lined bio-sensing film 118 laterally extend to cross boundariesof the channel region 120 and the source/drain regions 114, 116 topartially cover the source/drain regions 114, 116. The isolation layer144 may be, for example, silicon dioxide, a buried oxide (BOX) layer ofa SOI substrate, some other dielectric, or a combination thereof. Thebio-sensing film 118 lines the sensing well 146 and, in someembodiments, covers the isolation layer 144. Though not shown in FIG. 3, in some other embodiments, the bio-sensing film 118 may have openingsdepending on applications, for example, for external wiring pads.Further, the bio-sensing film 118 is configured to react with or bind tobiological entities to facilitate a change in the conductance of thechannel region 120, such that the presence of the biological entitiesmay be detected based on the conductance of the channel region 120. Thebio-sensing film 118 may be, for example, titanium nitride, titanium, ahigh κ dielectric, some other material configured to react with or bindto the biological entities, or a combination thereof. The biologicalentities may be, for example, DNA, ribonucleic acid (RNA), drugmolecules, enzymes, proteins, antibodies, antigens, or a combinationthereof. The bio-sensing film 118 may include a material for anyspecified bio-molecule binding. In an embodiment, the bio-sensing film118 includes a high-k dielectric material such as, HfO₂. In anembodiment, the bio-sensing film 118 includes a metal layer such as Pt,Au, Al, W, Cu, and/or other suitable metal. Other exemplary bio-sensingfilm 118 includes high-k dielectric films, metals, metal oxides,dielectrics, and/or other suitable materials. As a further example, thebio-sensing film 118 includes HfO₂, Ta₂O₅, Pt, Au, W, Ti, Al, Cu, oxidesof such metals, SiO₂, Si₃N₄, Al₂O₃, TiO₂, TiN, SnO, SnO₂; and/or othersuitable materials. The bio-sensing film 118 may include a plurality oflayers of material. The bio-sensing film 118 may, for example, have athickness of less than about 100 nanometers.

In some embodiments, the reference electrode 132 is disposed over thesensing well 146. In other embodiments, the reference electrode 132 maybe positioned indirectly or directly on the isolation layer 144laterally next to the sensing well 146. The reference electrode 132 mayalternatively be disposed indirectly or directly under the bio-sensingfilm 118. In some embodiments, the reference electrode 132 comprisesplatinum (Pt), gold (Au), silver (Ag), silver chlorine (AgCl) or thecombination thereof. The reference electrode 132 may have a thickness ina range of from about 500 Å to about 1 μm. By separating the referenceelectrode 132 from the device substrate 134, contamination introduced bythe reference electrode 132 is effectively prevented.

While the embodiment of FIG. 3 includes the back gate electrode 148 andthe gate dielectric layer 142, it is appreciated that the back gateelectrode 148 and the gate dielectric layer 142 may be omitted in otherembodiments. The sensing well 146 is exposed to a fluid 122. With thefluid 122 is applied to the bioFET device 130, a reference bias isapplied to the reference electrode 132.

During operation, a test sample is suspended within the fluid 122 andapplied to the sensing well 146 to detect the presence of the biologicalentities. Further, after application of the fluid 122 to the sensingwell 146, the fluid 122 may be biased to a reference potential toenhance the detection of the biological entities. The referenceelectrode 132 provides the fluid 122 a reference potential, for example,through an external power source which may be controlled by thecontroller 108.

FIG. 4 is a flow diagram illustrating a method for 3D analysis of a testsample such as a cell or group of cells using a 2D biosensor array, andFIGS. 5A-5C conceptually illustrate further aspects of the method ofFIG. 4 . In general, the illustrated method includes repositioning ofthe 3D test sample relative to the biosensor array so a plurality ofdifferent regions of the sample sequentially are placed in contact withthe sensor array for analysis. The data collected from each of thesample regions are then combined to obtain a 3D analysis of the testsample using a 2D sensor array. More particularly, the illustratedmethod 200 includes loading a test sample, such as a cell or group ofcells into the biosensor device 130 at a step 210. At step 212, the cellis “trapped” or placed on the biosensor array 102. As noted above, thebiosensor system 100 shown in FIG. 1 includes an electrode array 106configured to selectively apply various DEP forces for manipulating thetest sample relative to the sensor array 102. The controller 108 may beprogrammed or operated to apply the appropriate electrical signals tothe electrode array 106 to generate the desired DEP force.

Thus, in step 212 the sample is trapped using a positive DEP force insome examples. In other embodiments, the sample contacts the sensorarray 102 by gravity force. FIG. 5A illustrates a 3D test sample 250that includes a cell or group of cells. A first region 252 of the sampleor cell 250 contacts the sensor array 102. At step 214, analysis ordetection of the test sample 250 is conducted by the biosensor 102 toobtain test data regarding the first cell region 252 at step 216.

As noted above, a plurality of regions of the test sample are analyzedand the data are combined to generate a 3D analysis of the sample. Ifthere are additional regions of the test sample 250 for analysis asdetermined at step 220, the method proceeds to step 230. At step 230,the test sample 250 is lifted by a DEP force, such as a negative DEPforce such that the first region 252 shown in FIG. 5A is lifted off thebiosensor 102. FIG. 5B shows an arrow 256 representing the negative DEPthat lifts the sample 250 off the biosensor 102. In step 232 the sample250 is rotated by applying a rotating DEP force. As will be discussedfurther below, the controller 108 is operable to apply differentelectrical signals to the electrode array 106, such as a rotating ACsignal to apply the desired rotational force to the sample 250. In FIG.5B, the rotational force is represented by an arrow 258. The sample 250is rotated until a second region 254 is positioned for placement on thebiosensor array 102, as shown in FIG. 5B. In step 234 of FIG. 4 , thesample 250 is allowed to sink from its elevated position such that thesecond region 254 of the sample 250 contacts the biosensor 102 as shownin FIG. 5C. The method 200 then returns to step 212, where a positiveDEP is applied to trap the sample 250 on the biosensor 102. In someimplementations, gravity force is sufficient to situate the test sample250 on the biosensor 102 and step 212 may be omitted.

Once all of the test regions of the sample 250 have been analyzed asdetermined in step 220, the test data for each of the sample regions iscombined in step 222 to produce a 3D analysis of the 3D sample cell.

FIG. 6 is a top view illustrating aspects of the electrode array 106 andbiosensor array 102 of the biosensor system 100. In the illustratedexample the electrode array 106 includes two electrode groups orpatterns. A first electrode group 154 includes electrodes E1, E2, E3 andE4 situated in a common plane on respective four sides of the biosensorarray 102. A second electrode group 156 includes electrodes E5, E6, E7and E8, which are also situated in a common plane on the respective foursides of the biosensor array 102. In the illustrated example, the firstelectrode group 154 is positioned outside the second electrode group156, and both groups of electrodes 154, 156 are in the same plane. Otherembodiments may employ more or fewer electrodes in the electrode array.

FIG. 7 illustrates an example of further components of a biosensordevice 150 that includes the biosensor array 102 and electrode array106. FIG. 7 shows the reference electrode 132 of the bioFET device 130,which is configured to be situated over the sensor array 102 as will bediscussed further below. A microfluidics cover 152 is configured tocover the reference electrode 132 and the sensor array 102. Amicrofluidics wall further encloses the sides of the device 150 tocreate a microfluidic channel that contains the fluid 122 and receives atest sample that is positioned relative to the sensor array 102 foranalysis.

FIG. 8 is a side section view of the biosensor device 150 taken alongline A-A of FIG. 6 , including the sensor array 102 and electrode array106 of the backside sensing bioFET device 130 shown in FIG. 3 (not alldetails of the bioFET device 130 are shown in FIG. 8 for ease ofdiscussion). The biosensor device 150 includes the interconnectstructure 136 arranged over the handling substrate 138. In some examplesthe electrical interconnect structure provided in the interconnect layer136 is metal, though other conduct materials may alternatively be usedas noted hereinabove. The device substrate 134 is arranged over theinterconnect structure 136. The handling substrate 138 may be, forexample, a bulk semiconductor substrate, such as a bulk substrate ofmonocrystalline silicon and the substrate 134 may be, for example, asemiconductor layer of a semiconductor-on-insulator (SOI) substrate or abulk semiconductor substrate.

The isolation or BOX layer 144 is arranged over the device substrate134, and the reference electrode 132 is disposed over the biosensorarray 102. FIG. 8 illustrates portions of the electrode array 106,including sectional views of the electrodes E2 and E4 of the firstelectrode group 154 and electrodes E6 and E8 of the second electrodegroup 156. The electrodes E6, E8, may be fabricated from any suitableconductive material such as gold, platinum, carbon, etc. In theillustrated embodiment, the electrodes of both the first and secondelectrode groups 154, 156 are formed over the isolation layer 144 andare coplanar with one another. The electrodes further extend through theisolation layer 144 and the device substrate 134 to the interconnectlayer 136. The electrode array 106 is thus connectable to a voltagesource as controlled by the controller 108 to apply various signals tothe electrodes of the electrode array to manipulate a test sample suchas described in conjunction with FIGS. 4 and 5A-5C.

In the illustrated example, the electrode array 106 are configured toselectively move a test sample 250 so as to trap the test sample 250 onthe biosensor array 102, and to separate the test sample 250 from thebiosensor array 102 by a DEP force. FIGS. 9 and 10 illustrate thisconcept, where a positive DEP is generated as shown in FIG. 9 to movethe test sample 250 towards the biosensor array 102 and a negative DEPis generated in FIG. 10 to move the test sample 250 away from thebiosensor array 102. More particularly, the test sample 250, such as acell or group of cells, experiences a net force in the non-uniformelectric field and is pushed towards the field maxima (positive DEP) inFIG. 9 , or towards the field minimum (negative DEP) in FIG. 10 .

The magnitude of the positive and negative DEP can be modified by theactuation frequency of the AC signal applied to the electrodes.Referring now to FIG. 11 , the electrodes E5-E6 of the second or innerelectrode group 156 are configured for generating the positive DEP fortrapping the test sample 250 onto the biosensor array 102. Theelectrodes E1-E4 of the first electrode group 154 are floating, and eachof the electrodes E5-E8 of the second or inner electrode group 156 aregrounded. An actuation signal is applied from a voltage source 160 tothe reference electrode 132 to generate the positive DEP. The controller108 shown in FIG. 1 may be configured to control the voltage source 160.In the illustrated example, the reference electrode actuation signal VREis determined according to VRE=Vo*sin(w1t), where the AC signalfrequency w1 is selected to achieve an efficient positive-DEP to pushthe test sample 250 towards the biosensor array 102 to trap the testsample 250 on the biosensor array 102.

FIG. 12 illustrates applying an actuation signal to generate thenegative DEP to lift the test sample 250 off the biosensor array 102.The electrodes E5-E6 of the second or inner electrode group 156 areconfigured for generating the negative DEP lifting the test sample 250off the biosensor array 102 against gravity. The electrodes E1-E4 of thefirst electrode group 154 are again left floating, and each of theelectrodes E5-E8 of the second or inner electrode group 156 aregrounded. An actuation signal is applied from the voltage source 160 tothe reference electrode 132 to generate the negative DEP. In theillustrated example, the reference electrode actuation signal VRE isdetermined according to VRE=Vo*sin(w2t), where the AC signal frequencyw2 is selected to achieve an efficient negative DEP to lift the testsample 250 against gravity.

Additionally, the illustrated electrode array 106 (see FIG. 1 ) areconfigured to selectively rotate the test sample to align the desiredportion of the test sample with the biosensor array 102 as discussedabove. For instance, the illustrated electrode array 106 are energizedby the controller 108 to rotate the test sample about at least one of afirst axis, a second axis extending perpendicularly to the first axis,or a third axis extending perpendicularly to the first axis and thesecond axis. FIGS. 13-15 illustrate example arrangements for rotatingthe test sample 250 about these three axes. For instance, FIGS. 13-15illustrate X, Y and Z axes, with the X axis extending horizontally inand out of the drawing Figures, the Y axis extending perpendicularly tothe X axis in a left-right direction, and the Z axis extendingperpendicularly to both the X and Y axes in an up-down direction.

FIG. 13 illustrates an example where the electrode array 106 areconfigured, and actuation signals are applied, to rotate the test sample250 about the Z axis. In other words, the test sample is rotated about avertical axis after being lifted off the biosensor array 102 by thenegative DEP force as shown in FIG. 12 . In the example of FIG. 13 , theelectrodes E1, E2, E3 and E4 surround the biosensor array 102 and assuch are positioned on each of four sides of the biosensor array 102.Thus, as shown in FIG. 13 , the electrodes E1, E2, E3 and E4 are eachseparated from their adjacent electrodes by 90 degrees. In other words,the E1 electrode has a phase angle of 0, the E2 electrode has a phaseangle of 90 degrees, the E3 electrode has a phase angle of 180 degrees,and the E4 electrode has a phase angle of 270 degrees.

To energize the electrodes to move the test sample 250 about the Z axis,the inner electrode group 156 are not used, and thus the electrodesE5-E8 and the reference electrode 132 are all Floating. The controller108 is configured to apply voltages V1, V2, V3 and V4 to the electrodesE1, E2, E3 and E4, respectively, where the voltages V1-V4 are determinedaccording to

V1=Vo*sin(wt)

V2=Vo*sin(wt+0.5π)

V3=Vo*sin(wt+π)

V4=Vo*sin(wt+1.5π)

The AC signal frequency ω is determined based on the type of test sampleand the microfluidics fluid solution. In some embodiments, the AC signalfrequency is 10 k-50 MHz, for example.

FIG. 14 illustrates an example where the electrode array 106 areconfigured, and actuation signals are applied, to rotate the test sample250 about the X axis after being lifted off the biosensor array 102 bythe negative DEP force as shown in FIG. 12 . In the example of FIG. 14 ,the electrodes E1, E3, E5, and E7, as well as the reference electrode132 are not used and are thus floating. The electrodes E2 and E4 aregrounded. Voltages V6 and V8 are applied to the electrodes E6 and E8,respectively. The voltage signals V6 and V8 are determined according to

V6=Vo*sin(wt)

V8=Vo*sin(wt+θ),

Where θ is about 40-90 degrees depending on the particular electrodeshape and design.

FIG. 15 illustrates an example where the electrode array 106 areconfigured, and actuation signals are applied, to rotate the test sample250 about the Y axis after being lifted off the biosensor array 102 bythe negative DEP force as shown in FIG. 12 . In the example of FIG. 15 ,the electrodes E2, E4, E6, and E8, as well as the reference electrode132 are not used and are thus floating. The electrodes E1 and E3 aregrounded. Voltages V5 and V7 are applied to the electrodes E5 and E7,respectively. The voltage signals V5 and V7 are determined according to

V5=Vo*sin(wt)

V7=Vo*sin(wt+θ),

Where θ is about 40-90 degrees depending on the particular electrodeshape and design.

FIGS. 16-20 illustrate steps in a process for forming the electrodearray 106 of the biosensor device 150. The electrode array 106 areformed on the isolation layer 144 to surround the biosensor array 102 insome examples. FIGS. 16-20 illustrate the formation of one of theelectrode array 106 as an example. The remaining electrodes arefabricated similarly. In FIG. 16 , the bioFET array 102 including anarray of the dual-gate backside bioFET devices 130 illustrated in FIG. 3is provided. As disclosed above, the structure includes the interconnectstructure 136 arranged over the handling substrate 138, with the devicesubstrate 134 arranged over the interconnect structure 136. The handlingsubstrate 138 may be, for example, a bulk semiconductor substrate, suchas a bulk substrate of monocrystalline silicon. The device substrate 134accommodates the biosensor array 102 and may be, for example, asemiconductor layer of a semiconductor-on-insulator (SOI) substrate or abulk semiconductor substrate. The isolation or BOX layer 144 is arrangedover the device substrate 134 with the sensing film 118 disposed on thedevice substrate 134. In the illustrated examples, the electrode array106 connect to other structures such as the controller 108 and variousvoltage sources through the interconnect layer 136. In FIG. 16 , anopening 170 extends through the sensing film 118, the isolation layer144 and the device substrate 134 to a conductive pad 172 in theinterconnect layer 136.

As shown in FIG. 17 , a metal layer 174 is deposited over the sensingfilm 118, for example, by a metal sputtering process. The conductivelayer lines the opening 170, and may include metal materials such asplatinum (Pt), gold (Au), silver (Ag), silver chlorine (AgCl) or thecombination thereof. In FIG. 18 , a photoresist (PR) mask 176 isdeposited over the conductive layer 174 and patterned. The PR mask ispatterned to be an etch mask to etch the metal layer 170. A typicallithographic process may be used to deposit the PR mask, cure thephotoresist, expose the photoresist to patterned light, and develop thephotoresist to create a desired pattern.

In FIG. 19 , an etch process removes portions of the metal layer 174 inaccordance with the PR mask 176. The etch process may be a dry etch. Thedry etch may use a chlorine based or a fluorine based etchant in aplasma process. In one embodiment, the etch process utilizes an endpoint system where the etch process detects an end point material, forexample, IMD material, and signals that the end point for the etch hasbeen reached. At the end point, the etch process continues for a definedduration to over etch an additional amount of material to ensurecomplete removal of conductive material of the metal layer 174. In FIG.20 , the PR mask 176 is removed to expose the formed electrode pattern106.

Disclosed examples thus provide biosensor systems and methods thatgather data for a 3D analysis of a 3D test sample, such as a cellculture. Such 3D analysis may provide additional, more relevantinformation regarding the test sample. An array of 2D biosensors is ableto gather 3D information regarding a 3D test sample by repositioning thetest sample relative to the biosensor to gather data on several segmentsof the test sample. These data are then combined to provide the 3Danalysis.

In accordance with some disclosed embodiments, a biosensor systemincludes an array of biosensors with a plurality of electrodes situatedproximate the biosensor. A controller is configured to selectivelyenergize the plurality of electrodes to generate a DEP force toselectively position a test sample relative to the array of biosensors.

In accordance with further embodiments, a biosensor system includes ahandling substrate, an interconnect layer over the handling substrate,and a device substrate over the interconnect layer. The device substratehas a biosensor array electrically connected to the interconnect layer.An isolation layer is over the device substrate. A plurality ofelectrodes are formed over the isolation layer and extend through theisolation layer and the device substrate to the interconnect layer. Theplurality of electrodes are configured to receive an AC signal toestablish a DEP force to selectively position a test sample relative tothe biosensor array.

In accordance with still further examples, a method includes providing abiosensor array and a 3D test sample. Data regarding a first segment ofthe 3D test sample is collected by the biosensor array. A DEP force isgenerated to reposition the 3D test sample relative to the biosensorarray, and data regarding a second segment of the 3D test sample iscollected by the biosensor array. The data regarding the first andsecond segments of the 3D test sample are then combined.

This disclosure outlines various embodiments so that those skilled inthe art may better understand the aspects of the present disclosure.Those skilled in the art should appreciate that they may readily use thepresent disclosure as a basis for designing or modifying other processesand structures for carrying out the same purposes and/or achieving thesame advantages of the embodiments introduced herein. Those skilled inthe art should also realize that such equivalent constructions do notdepart from the spirit and scope of the present disclosure, and thatthey may make various changes, substitutions, and alterations hereinwithout departing from the spirit and scope of the present disclosure.

What is claimed is:
 1. A biosensor system, comprising: a handlingsubstrate; an interconnect layer over the handling substrate; a devicesubstrate over the interconnect layer, the device substrate including abiosensor array electrically connected to the interconnect layer; anisolation layer over the device substrate; a plurality of electrodesformed over the isolation layer and extending through the isolationlayer and the device substrate to the interconnect layer, the pluralityof electrodes configured to receive an AC signal to establish a DEPforce to selectively position a test sample relative to the biosensorarray.
 2. The biosensor system of claim 1, wherein the plurality ofelectrodes include: first, second, third and fourth electrodespositioned on respective first, second, third and fourth sides of thebiosensor array; fifth, sixth, seventh and eighth electrodes positionedon the respective first, second, third and fourth sides of the biosensorarray; and a reference electrode positioned above the first, second,third, fourth, fifth, sixth, seventh and eighth electrodes, and thebiosensor array.
 3. The biosensor system of claim 2, wherein the ACsignal includes a first AC signal having a first predetermined frequencyand a second AC signal having a second predetermined frequency, whereinthe reference electrode is configured to receive the first AC signal toestablish a positive DEP to trap the test sample on the array ofbiosensors, and the reference electrode is configured to receive thesecond AC signal to establish a negative DEP to separate the test samplefrom the array of biosensors.
 4. The biosensor system of claim 2,wherein the AC signal includes a first AC signal having a 0 degree phaseangle, a second AC signal having a 90 degree phase angle, a third ACsignal having a 180 degree phase angle, and a fourth AC having a 270degree phase angle, and wherein the first electrode is configured toreceive the first AC signal, the second electrode is configured toreceive the second AC signal, the third electrode is configured toreceive the third AC signal, and the fourth electrode is configured toreceive the fourth AC signal to establish a DEP force to rotate the testsample about a first axis.
 5. The biosensor system of claim 4, whereinthe AC signal has a predetermined frequency.
 6. The biosensor system ofclaim 4, wherein the sixth electrode is configured to receive a fifth ACsignal having a first phase angle, and the eighth electrode isconfigured to receive a sixth AC signal having a second phase angle toestablish a DEP force to rotate the test sample about a second axisperpendicular to the first axis.
 7. The biosensor system of claim 1,wherein the array of biosensors includes a plurality of backside sensingbioFETs.
 8. A method, comprising: providing a biosensor array; providinga three-dimensional (3D) test sample; collecting data regarding a firstsegment of the 3D test sample by the biosensor array; generating a DEPforce to reposition the 3D sample relative to the biosensor array;collecting data regarding a second segment of the 3D test sample by thebiosensor array; combining the data regarding the first and secondsegments of the 3D test sample.
 9. The method of claim 8, whereingenerating a DEP force includes generating a positive DEP force to trapthe test sample on the biosensor array.
 10. The method of claim 8,wherein generating a DEP force includes generating a negative DEP forceto lift the test sample off the biosensor array.
 11. The method of claim8, wherein generating a DEP force includes generating a rotating DEPforce to rotate the test sample about a predetermined axis.
 12. Themethod of claim 8, wherein generating a DEP force includes generating arotating DEP force to rotate the test sample about at least one of afirst axis, a second axis extending perpendicularly to the first axis,or a third axis extending perpendicularly to the first axis and thesecond axis.
 13. The method of claim 8, wherein generating a DEP forceincludes selectively energizing a plurality of electrodes positionedproximate the biosensor array.
 14. The method of claim 13, whereinselectively energizing the plurality of electrodes includes applying apredetermined AC signal to at least one of the plurality of electrodes.15. The method of claim 14, wherein the predetermined AC signal has apredetermined frequency.
 16. A biosensor system, comprising: a handlingsubstrate; an interconnect layer over the handling substrate; a devicesubstrate over the interconnect layer, the device substrate including abiosensor array electrically connected to the interconnect layer; anisolation layer over the device substrate; a plurality of electrodesformed over the isolation layer and extending through the isolationlayer and the device substrate to the interconnect layer, the pluralityof electrodes being positioned on four sides of the array of biosensors.17. The biosensor system of claim 16, wherein the plurality ofelectrodes configured to receive an AC signal to establish adielectrophoresis (DEP) force to selectively position a test samplerelative to the biosensor array.
 18. The biosensor system of claim 16,wherein the plurality of electrodes include: first, second, third andfourth electrodes positioned on a common plane on respective first,second, third and fourth sides of the array of biosensors; fifth, sixth,seventh and eighth electrodes positioned on the common plane on therespective first, second, third and fourth sides of the array ofbiosensors; and a reference electrode positioned above the first,second, third, fourth, fifth, sixth, seventh and eighth electrodes, andthe array of biosensors.
 19. The biosensor system of claim 16, whereinthe array of biosensors includes a plurality of backside sensingbioFETs.
 20. The biosensor system of claim 17, further comprising acontroller configured to selectively energize the plurality ofelectrodes to generate DEP force to selectively position a test samplerelative to the biosensor array.